1. Field of the Invention
The present invention relates generally to heating with electromagnetic wave energy in a conductive cavity, and more particularly, pertains to an antenna assembly including a directional rotating antenna, an antenna rotor, an antenna rotating assembly, and a grease shield for directing air flow velocity to drive the antenna rotor to axially rotate the directional antenna axially supported by the antenna rotating assembly.
2. Description of the Prior Art
Prior art microwave ovens suffer from nonuniform energy distribution, and more particularly, nonuniform heating patterns depending upon the type of particular product, which usually is food, being heated. The nonuniform heating pattern occurs because of the unequal distribution of microwave energy coupled into a conductive cavity of a microwave oven from a source of microwave power such as a magnetron, from the reflections of microwave energy from the product within the microwave oven cavity, and the conductive sidewalls framing the microwave oven cavity. Multiple reflections within the conductive microwave oven cavity occur and produce configurations of the electromagnetic fields referred to as modes. These reflections cause constructive and destructive interference at and in different parts of the product being heated, and therefore, result in hot areas intermixed with cold areas. Where the product is food, the result is overcooked areas of the food intermixed with undercooked areas of the food.
Some food products which have been particularly difficult to cook in the prior art microwave ovens include yeast products such as breads; baked products such as cakes and pies; scattered products such as cookies, appetizers, and hors d'euvres, and; egg dishes such as custards and quiches. All of these types of food products when cooked in the prior art microwave ovens have exhibited overcooked areas intermixed with undercooked areas leaving much to be desired in the cuisine of the consuming gourmet.
The prior art processes for improving the nonuniform energy distribution patterns in the prior art microwave ovens have been mode stirring which attempts to randomize reflections by introducing a time varying scattering of the microwave energy; utilizing a turntable within the microwave oven cavity to rotate the product about a vertical axis within the microwave oven separately or in combination with a mode stirrer; and, utilizing rotatable antennas within the microwave oven cavity.
The prior art process of utilizing rotatable antennas or exciters within the microwave oven cavity has been deficient from the point that rotatable antennas or exciters within the microwave oven cavity failed to achieve a uniform energy distribution and complex mechanical structure has been required to support and rotate the antennas.
In rotating physical structures within the microwave oven cavity, a rotating mechanism such as an electric motor was required along with suitable mounting of the motor, isolating the motor and shaft from the electromagnetic field within the microwave oven cavity, and providing additional energy to power and drive the electric motor. Further, the prior art rotation assemblies of either turntables or antennas were always subject to mechanical breakdown and in the event of mechanical breakdown, a skilled serviceman was required to service the mechanical working components of the microwave oven.
The present invention provides a microwave oven having a uniform energy distribution pattern and overcomes the disadvantages of the prior art microwave ovens.